A Sengoku-Era Castle Site with Panoramic Views of Lake Nakaumi
Tokamiyama Castle was a Japanese mountain fortress that once stood on the summit of Mt. Tokamiyama in what is now Shintokamicho, Yasugi City, Shimane Prefecture. During the Sengoku period, it served as an important strategic stronghold in the Izumo region.
The castle was built on the approximately 92-meter-high Mt. Tokamiyama overlooking Lake Nakaumi. From this elevated position, the fortress could monitor water traffic and transportation routes around the lake, making it an important defensive and strategic location.
Today, the area around the former castle site has been developed as Tokamiyama Nagisa Park. The park is a popular place for local residents to relax and also offers visitors opportunities for hiking, historical exploration, and scenic views.
From near the summit, visitors can look across Lake Nakaumi and the mountains of the Shimane Peninsula. On clear days, Mt. Daisen can also be seen in the distance. The landscape has long been regarded as one of the symbolic views of Yasugi.
Mt. Tokamiyama is an isolated, almost cone-shaped mountain located on a peninsula-like area extending into the eastern part of Lake Nakaumi. In ancient times, the mountain was known as Tokamijima and was recorded under this name in the Izumo no Kuni Fudoki, an ancient record of the Izumo region.
The mountain was once surrounded by water and formed an island. Over many centuries, sediment accumulated around it, and land reclamation carried out during the Edo period eventually connected it to the mainland.
This unusual geographical setting also gave Tokamiyama considerable military value. With water surrounding three sides of the mountain, approaching enemies could be spotted relatively easily. Its location also made it possible to monitor boats traveling across Lake Nakaumi.
The mountain additionally served as a natural breakwater for Yasugi Port, making the surrounding area an important center for transportation and economic activity from ancient times.
Tokamiyama Castle is believed to have been constructed during the Muromachi period by the Matsuda clan, a powerful warrior family in the Izumo region. The castle took the form of a hilltop fortress, with defensive structures arranged around the summit.
The main enclosure, or honmaru, occupied the summit, while a series of smaller fortified enclosures known as kuruwa were positioned along the surrounding ridges and peaks.
Although many of these enclosures were relatively small, they made effective use of the mountain’s natural terrain. The layout provides a good example of the defensive characteristics of Japanese mountain castles during the Sengoku period.
On the southern side of the mountain, a series of fortified enclosures followed both sides of a valley, creating a continuous defensive line leading toward the main enclosure. The area around this valley is thought to have contained the castle lord’s residence and may have served as a center for both administration and daily life within the fortress.
During the turmoil surrounding the Onin War, the Matsuda clan was driven from the castle. Tokamiyama Castle subsequently came under the control of the Amago clan, the powerful Sengoku warlords who ruled much of the Izumo region.
The Amago clan established their main stronghold at Gassan Toda Castle and constructed a network of subsidiary fortresses to protect their territory. Tokamiyama Castle was counted among the “Ten Fortresses of the Amago Clan”, forming an important part of this defensive network.
Because of its position overlooking Lake Nakaumi, the castle also functioned as a strategic water-based stronghold. Warriors such as Matsuo Tōtōmi-no-kami are said to have been stationed here, and the castle reportedly served as a naval base supporting Gassan Toda Castle.
Tokamiyama Castle became the scene of repeated battles during the wars of the Sengoku period.
In 1468, Matsuda Bingo-no-kami joined forces with the Yamana clan and opposed Amago Kiyosada. The castle was eventually attacked by the Amago forces and fell.
Tokamiyama Castle was later maintained as an Amago stronghold. However, in 1566, it was attacked by forces led by Kodama Naritada, a commander of the Mori clan’s naval forces, and the castle fell once again.
In 1569, an army attempting to restore the Amago clan, led by Yamanaka Yukimori and others, invaded Izumo. Tokamiyama Castle once again became an Amago stronghold.
However, after the Amago restoration army suffered a major defeat against the Mori forces at the Battle of Fuseyama the following year, Tokamiyama Castle was surrendered. Its role in the turbulent history of the Sengoku period then came to an end.
Mt. Tokamiyama is more than a former castle site. It has long been familiar to the people of Yasugi as one of the area’s characteristic landmarks.
The mountain is even mentioned in the famous local folk song Yasugi-bushi, which includes the line:
“Yasugi, the place of a thousand shops, famous for its Shajitsu cherry blossoms and Mt. Tokamiyama.”
The mountain is also associated with local mythology. During Kan-zuki, the traditional “month when the gods are present” in Izumo, when deities from throughout Japan are said to gather in the region, it is believed that the gods traveling toward Izumo stopped to rest on Mt. Tokamiyama.
Because of this tradition, there was reportedly once a local custom of avoiding climbing Mt. Tokamiyama during the tenth month of the traditional lunar calendar.
During the Edo period, a man named Bokura Magosaburo is said to have planted many cherry trees on Mt. Tokamiyama. As a result, the mountain became known as a beautiful cherry blossom viewing destination in spring.
Today, visitors can still enjoy the combination of spring cherry blossoms and the historic mountain castle landscape. The summit can be reached in approximately 10 minutes from the trailhead, making the mountain a popular destination for a short and relatively easy hike.
In 1993, the area around Mt. Tokamiyama was developed as Tokamiyama Nagisa Park. The park includes walking trails and observation areas and is used by local residents as a place for camping, outdoor activities, and recreation.
Near the summit, visitors can enjoy views across the calm waters of Lake Nakaumi, the mountains of the Shimane Peninsula, and, in clear weather, the distant peak of Mt. Daisen, one of the most prominent mountains in the Chugoku region.
Standing in this landscape offers an opportunity to imagine the views once observed by the warriors who defended the castle centuries ago.
The area surrounding Mt. Tokamiyama also contains archaeological sites and burial mounds dating from the Yayoi to Kofun periods. These remains indicate that people had already lived in the area in ancient times and that the location played an important role in the region’s history long before the castle was built.
Tokamiyama Castle is one of the more easily accessible historic sites in Yasugi. From JR Yasugi Station, it takes approximately 10 minutes on foot to reach the trailhead, followed by another roughly 10-minute climb to the summit.
Although the hike is short, visitors can experience a combination of history, nature, and panoramic scenery in a single outing. Walking through the former castle grounds while looking across Lake Nakaumi provides an evocative way to discover the history and culture of Yasugi.
Tokamiyama Castle is a valuable reminder of the Sengoku history of the Izumo region and an important part of the cultural landscape of Yasugi. Its strategic location, connection with the Amago clan, and dramatic history of repeated battles reveal the importance of Lake Nakaumi and its surrounding transportation routes during Japan’s age of civil war.
At the same time, Mt. Tokamiyama remains deeply connected with the everyday life and culture of the people of Yasugi. From cherry blossoms in spring to sweeping views across Lake Nakaumi, the former castle site offers travelers a chance to combine a short hike with an exploration of local history, legends, and scenery.